You need to analyze the best keywords that will fit your site. Check on the keywords search volume and you'll get a probability stats on the traffic amount,but if it's too competitive, you'll be needing a lot of work to do to beat your competitors
just think simply on your topic what word comes to your mind first could be the best; but be careful it should not be much similar with others. it should be simple and unique.
unfortunately for good earning you need use high paying key words use keyword tools to get rich keywords or search on Google with " top paying keyworfd"
The best keywords are 2- to 4-word phrases that accurately describe what you offer using everyday language that searchers are likely to type in, and which aren't so competitive that you have no chance of getting on the front page. If your keywords are too general then they'll likely be too competitive, and even if you rank well on them your traffic might not convert well, since searchers are usually looking for something specific.
Its depends on your website first make one then try to check with google keyword tool and do competitive research to get the best answers.